you can not install the airports from the WorldHub, those will be added to the abse game with future updates. For now you can not even build the airport you are currently working on with the Scenery Editor for further ingame tests.
Seems not true to me - hit the “build all” button, and copy the compiled project to your Community folder. Works! What you can’t do, is excluding the original default airport. Thus, expect some anomalities.
you used the downloaded source from the WorlHub? When i used the source from the world hub during the first weeks There was no “build” option enabled. Only the save option was enabled.
The build option is in the project editor, not in the scenery editor. It worked serveral times for me. Maybe you have closed the project editor window?